OPEC does see electric vehicles getting cheaper and better, just not enough to compete with the ever-improving (read: more fuel efficient) gasoline cars. OPEC predicts that, "The cost of technologies such as electric batteries for cars will be further reduced in the coming decades – probably by 30–50% – while, at the same time, performance will improve. However, without major breakthroughs in battery technology, the concept of plug-in battery electric cars may not achieve mass market appeal due to the many inconveniences and consumer reservations." OPEC doesn't spell out what those "many inconveniences" are, but perhaps our readers can give us some suggestions.
OPEC also says that, "Without a technology breakthrough, battery electric vehicles are not expected to gain significant market share in the foreseeable future" (page 12 in this PDF). It's not the most original sentiment because it's mostly a cut-and-paste job from last year, where OPEC wrote that, "pure plug-in electric cars are unlikely to gain a significant market share in the foreseeable future" (page 102 in this PDF).
Overall, the message is that fossil fuels will continue to dominate the transportation landscape for a long time to come. The only non-gasoline technology that OPEC thinks might have a chance to make a dent in gasoline usage is CNG, but even then OPEC only says that CNG offers a, "significant unknown."
If you'd like to explore the 2015 WOO for yourself, you can look through the interactive version here.